1.Easy
A crate is pulled 3 m along a level floor by a rope that makes 35° with the horizontal. The tension in the rope is 50 N. Find the work W done by the rope on the crate.
F = 50 Nd = 3 mθ = 35°
W = J
Work & energy worksheet with answers
2.Easy
A 2 kg ball is dropped from rest from a height of 17 m. Ignore air resistance. Find its speed v just before it hits the ground.
m = 2 kgh = 17 mg = 9.81 m/s²
v = m/s
3.Medium
A 2.5 kg block slides 15 m down a slope at 30° to the horizontal, with a coefficient of kinetic friction of 0.25. Find the work Wf done against friction.
m = 2.5 kgθ = 30°μ = 0.25d = 15 mg = 9.81 m/s²
Wf = J
4.Medium
An 800 kg car drives up a 6° slope at a constant 54 km/h. Air resistance and rolling resistance together amount to 200 N. Find the power P the wheels must deliver, in kW.
m = 800 kgθ = 6°Fr = 200 Nv = 54 km/hg = 9.81 m/s²
P = kW
5.Hard
A 0.5 kg block is released from rest at height 3 m on a smooth ramp. At the bottom it crosses a rough horizontal strip 2.5 m long (μ = 0.25) and then runs onto a spring (k = 500 N/m) on a smooth surface. Find the speed v of the block when it reaches the spring.
m = 0.5 kgh = 3 mL = 2.5 mμ = 0.25k = 500 N/mg = 9.81 m/s²
v = m/s
6.Hard
A 4 kg block rests on a rough horizontal table (μ = 0.1). A light string runs from it over a smooth pulley at the edge of the table to a hanging 5 kg block. The system is released from rest. Find the speed v of the blocks after the hanging block has dropped 0.5 m.
m1 = 4 kgm2 = 5 kgμ = 0.1d = 0.5 mg = 9.81 m/s²
v = m/s
Answer key
- 1. W = 122.9 J
- 2. v = 18.26 m/s
- 3. Wf = 79.65 J
- 4. P = 15.31 kW
- 5. v = 6.826 m/s
- 6. v = 2.239 m/s
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